Endo alicyclic end capped polyimidazopyrrolone

ABSTRACT

1-Y2,2-Y3,3-Y4,4-Y5,5-Y6,5-Y7,6-(Z2-Z1-),6-Y1,1,4-(-X-)- RESINS HAVING HIGH TEMPERATURE STABILITY CAN BE MADE BY CURING CHEMICALLY STABLE ALICYCLIC ENDO END CAPPED AROMATIC PREPOLYMERS. THE PERPOLYMERS CAN BE MADE BY REACTING PROPER STOICHIOMETRIC AMOUNTS OF TETRAACIDS OR DERIVATIVES WITH AN AROMATIC TETRAAMINE, AND AN END CAPPING COMPOUND HAVING THE FORMULA     CYCLOHEX-2-ENE   WHEREIN Y1-Y6, INCLUSIVE, CAN BE HYDROGEN, HALOGEN, NITRO, ARYL, ALKYL, ALKYL ETHER, OR ALKARYL; X CAN BE CARBONYL, OXYGEN, SULFUR, METHYLENE, HALOGEN SUBSTITUTED METHYLENE, ALKYL SUBSTITUTED METHYLENE, OR ARYL SUBSTITUTED METHYLENE; Z1 CAN BE AN ARYLENE OR AN ALKYLENE GROUP HAVING 0 TO 1 CARBON ATOMS; Z2 CAN BE AN ISOCYANATE RADICAL OR AN AMINE RADICAL; AND Y7 CAN BE AN ISOCYANATE RADICAL OR AMINO IN A STABLE COMBINATION WITH Y6. THE END CAPPING COMPOUND CAN BE SYNTHESIZED BY REACTING A CYCLO DIOLEFIN WITH AN OLEFINIC COMPOUND ACCORDING TO A DIELS-ALDER REACTION.

United States Patent Oflice Patented July 24, 1973 Synthesis of compounds similar to the alicyclic endo 3,748,310 I compounds used herein have been disclosed by Diels and ENDO ALICYCLIC END CAPPED Alder in US. Pat. 1,944,731. These compounds are pro- POLYIMIDAZOPYRROLONE duced by reacting a diene with a dienophile to produce 8.

Eugene A. Burns, Palos Verdes Peninsula, and Robert J. 5 six membered ring compound Jones, Hermosa Beach, Calif., assignors to TRW Inc.,

Redondo lleach, Calif. 972 s N 2 0 832 SUMMARY OF THE INVENTION No if gi g g h 4 The high temperature aromatic resins of this invention CL 260 73.4 R 14 Claims are produced by reacting an aromatic tetraamine with a tetracarboxylic acid or derivative and end capping the polymer chain with a substitute alicyclic endo compound.

ABSTRACT OF THE DISCLOSURE The polymer chain which is produced by reacting stoi- Resins having high temperature stability can be made chiometric amounts of a tetraacid or derivative and the by curing chemically stable alicyclic endo end capped tetraamine is end capped with a substituted alicyclic endo aromatic prepolymers. The prepolymers can be made by 15 compound having the formula: reacting proper stoichiometric amounts of tetraacids or Y2 derivatives with an aromatic tetraamine, and an end m capping compound having the formula Y: Y4 i Y Y7 Y /I\Y1 z -z, Y5

X wherein Y Y inclusive, may be selected from hydrogen, Y4 I Y0 Y1 halogen, nitro, aryl, alkyl having 1 to 6 carbon atoms, Y6 alkyl ether having 1 to 6 carbon atoms, or alkaryl; X may be selected from any of carbonyl, oxygen, sulfur, methyl- Wherein 1 6a inclusive, Call be hydrogen, halogen, nitro, ene, halogen substituted methylene, alkyl substituted y alkyl, alkyl ether, y X can be carbonyl, methylene, or aryl substituted methylene; Z is an arylene Y Sulfur, methylfine, halogen Substituted methylene, or an alkylene radical having 0 to 1 carbon atoms; Z

alkyl substituted methylene, or aryl substituted methylene; may b l t d f any f; N1-1 or N=C=0 nd 1 can be all arylene an alkylene group havlIlg 0 to Y7 can be selected from an isocyanate radical or amino 1 carbon atoms; Z can be an isocyanate radical or an di L amine radical; and Y-; can be an isocyanate radical or The end capping endo compound is produced by 21 amino in a Stable combination with s- The end pp g Diels-Alder reaction wherein a cyclo diolefin having a compound can be synthesized by reacting a cyclo diolefin f l with an olefinic compound according to a Diels-Alder Y: reaction. 4

YaC: BACKGROUND OF THE INVENTION /x The present invention relates to stable, high tempera- Y4C=O ture aromatic resins. Resins, according to this invention,

are produced by a pyrolytic polymerization of prepolymers having reactive terminal groups. Pyrolytic polymerization is the coreaction of the reactive groups located at the terminal ends of the prepolymer upon heating at elevated temperature to cause chain extension and crosslinking of the prepolymer segment.

wherein Y -Y inclusive, may be selected from any of hydrogen, halogen, nitro, aryl, alkyl having 1 to 6 carbon atoms, alkyl ether having 1 to 6 carbon atoms, alkaryl; and X may be selected from any of carbonyl, oxygen, sulfur, methylene, halogen substituted methylene, alkyl substituted methylene or aryl substituted methylene is Polylmlde resms havmg been Produced by the Pyrolyne reacted with an olefinic compound having the formula: polymerization reaction of a polyimide prepolymer having end caps of bicyclo (2.2.1)hept-5-ene-2,3-anhydride as Y disclosed in US. Pat. 3,528,590. The polyimide prepoly- 7 l l was Produced 3 reacting a diemine with a l wherein Y and Y may be selected from any of hydrogen, e and end Capping the chem wlth a monoanhydnde halogen, nitro, aryl, alkyl having 1 to 6 carbon atoms, havmg the structure: alkyl ether having 1 to 6 carbon atoms, or alkaryl; Y-, may be selected from an isocyanate radical or amino R radical; Z is an arylene or an alkylene radical having 0 to 1 carbon atoms; and Z may be selected from any 0 of --NH or N=C=O. The prepolymers of this invention are made by reacting R C a tetraacid or derivative with a tetraamine and end cap- 8 ping the prepolymer with an alicyclic endo diamine or diisocyanate compound which may be illustrated ideally where R is hydrogen or an alkyl group. as follows:

where R; is a tetravalent aliphatic or aromatic radical, R is a tetravalent aromatic radical, and the n is an integer from 1 to 20.

Product properties of the cured polymer can be enhanced by the inclusion of olefinic crosslinking agents in amounts up to about 10% by weight of the resin at initiation of cure.

DISCLOSURE OF THE INVENTION High temperature resins of this invention are made by curing prepolymers prepared by reacting stoichiometric amounts of an aliphatic or aromatic tetraacid or derivative with an aromatic tetraamine and end capping the prepolymer with an alicyclic endo diarnine or diisocyanate compound. The prepolymers are characterized in that they are self-stable solids which react through the alicyclic endo compound to form a polymer having good properties in the temperature range of 300 C.-400 C. One of the chief advantages of these resins, in addition to their excellent physical and thermal properties, is the relative ease with which laminated or molded articles may be fabricated from them. Thus, rather than fabricating articles from a liquid resin, fabricators may form the solid prepolymers of this invention from the liquid starting materials and fabricate the articles from a dry or slightly tacky prepolymer. The savings in cleanup time and materials is substantial without sacrifice of product properties.

Alicyclic endo end cap compounds are synthesized by reacting a cyclodiolefin having the formula:

wherein Y -Y inclusive, may be selected from any of hydrogen, halogen, nitro, alkyl having 1 to 6 carbon atoms, alkyl ether having 1 to 6 carbon atoms, or alkaryl; and X may be selected from any of carbonyl, oxygen, sulfur, methylene, halogen substituted methylene, alkyl substituted methylene, or aryl substituted methylene, with an olefinic compound having the formula:

wherein Y and Y are selected from the same groups represented by Y -Y Y is selected from an isocyanate radical or an amino radical; Z is an arylene or an alkyl ene radical having 0 to 1 carbon atoms; and Z may be 4 selected from any of: --NH or N=C=O. Ideally, the reaction may be represented as follows:

wherein Y Y X, 2,, and 2;, have been identified above. The reaction is carried out in a liquid solvent, such as benzene, and temperatures of the reaction may range from room temperature to about 200 F.

Special note should be made of the alicyclic endo diisocyanate or diamine compound because they can be synthesized for instance, by Curtius reaction, rather than by Diels-Alder reaction. According to the Curtius reaction, an alicyclic endo diacid or derivative is reacted with ammonia or hydrazine according to the following reaction:

The following table provides a list of a few of the representative cyclodiolefin compounds which are suitable for reaction to produce the alicyclic endo end cap compounds.

TABLE I furane cyclopentadieneone 3,4diphenylthiophene cyclopentadiene methylcyclopentadiene 1,1,2,3,4,5-hexachlorocyclopentadiene The following table provides a list of a few of the representative olefinic compounds which are suitable for reaction to produce the alicyclic endo end cap compound.

TABLE II 1,3-allyl diisocyanate ethylene diisocyanate One of the resins according to this invention may be produced by reacting proper stoichiometric amounts of an aliphatic or aromatic tetraacid or dianhydride with an alicyclic endo diamine or diisocyanate at temperatures ranging from about 10 C. to about 200 C., and subsequently, or simultaneously, the mixture is reacted with an aromatic tetraamine in the presence of a dehydrating agent at temperatures ranging from about l8 C. to about 200 C. The reaction may be illustrated ideally as follows:

wherein Y -Y inclusive, may be selected from hydrogen, halogen, nitro, alkyl having 1 to 6 carbon atoms, aryl, alkyl ether having 1 to 6 carbon atoms, or alkaryl; X may be carbonyl, oxygen, sulfur, methylene, halogen substituted methylene, alkyl substituted methylene, or aryl substituted methylene; Z may be an arylene or an alkylene radical having to 1 carbon atoms; R, is a tetravalent aliphatic or aromatic radical; R is a tetravalent aromatic radical; and n is an integer from 1 to 20.

Closure of the imidazopyrrolene ring is eifected by a dehydrating in situ, i.e. simultaneously with the reaction of the constituents. The ring closure and prepolymer formation reactions must be carried out at temperatures below the polymer reaction temperature, i.e. below about 230 C.

Dehydrating agents used to facilitate the ring closure in the prepolymer reaction may be selected from organic anhydrides, such as acetic anhydride, and also, inert moisture adsorbing agents such as molecular sieves. Organic dehydrating agents are preferred because of their ease of removal from the resin product of the dehydration reaction. Of course, dehydrating agents are not required when using diisocyanates, however, more severe reaction conditions are required.

While the prepolymers may be synthesized from any aliphatic or aromatic dianhydride and any aromatic tetraamine, the compounds must be capable of reacting together and must remain stable at about 700 C. once they have reacted.

Examples of several typical aromatic tetraamines which may be used in this invention are:

TABLE III 3,3'-diaminobenzidine l,2,3,5-tetraaminobenzene 3,3',4,4'-tetraaminodiphenyl ether 3,3',4,4'-tetraaminodiphenyl methane 3,3,4,4'-tetraaminodiphenyl sulfone 3,3,4,4'-tetraamino benzophenone 2,3,6,7-tetraamino naphthalene 2,3,5,6-tetraamino indene 3,3,4,4'-tetraaminodiphenyl ethane 3,3',4,4'-tetraaminodiphenyl propane Examples of several specific dianhydrides are listed in the following table:

TABLE IV pyromellitic dianhydride benzophenone tetracarboxylic dianhydride 2,3,6,7-naphthalene tetracarboxylic dianhydride 3,3',4,4'-diphenyl tetracarboxylic dianhydride 1,2,5,6-naphthalene tetracarboxylic dianhydride 2,2,3,3'-diphenyl tetracarboxylic dianhydride 2,2-bis(3,4-dicarboxyphenyl) propane dianhydride bis(3,4dicarboxyphenyl) sulfone dianhydride 3,4,9,10-perylene tetracarboxylic dianhydride bis (3,4-dicarboxyphenyl) ether dianhydride ethylene tetracarboxylic dianhydride naphthalene-1,2,4,5-tetracarboxylic dianhydride naphthalene-1,4,5Q8-tetracarboxylic dianhydride decahydronaphthalene-1,4,5,8-tetracarboxylic dianhydride 4,S-dimethyl-1,2,3,5,6,7-hexahydronaphthalenel,2,5,6-tetracarboxylic dianhydride 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride 2,3,6,7-tetrachloronaphthalene-l,4,5,8-tetracarboxylic dianhydride phenanthrene-1,8,9,l0-tetracarboxylic dianhydride cyclopentane-l,2,3,4-tetracarboxylic dianhydride pyrrolidine2,3,4,5-tetracarboxylic dianhydride pyrazine-2,3,5,6-tetracarboxylic dianhydride 2,3-bis(2,3-dicarboxyphenyl) propane dianhydride 1,l-bis(2,3-dicarboxyphenyl) ethane dianhydride 1,1-bis(3,4-dicarboxyphenyl) ethane dianhydride bis (2,3-dicarboxyphenyl) methane dianhydride bis(3,4-dicarboxyphenyl) methane dianhydride bis(3,4-dicarboxyphenyl) sulfone dianhydride bis(3,4-dicarboxyphenoxyphenyl) sulfone dianhydride benzene-1,2,3,4-tetracarboxylic dianhydride 1,2,3,4-butane tetracarboxylic dianhydride thiophene-2,3,'4,5-tetracarboxylic dianhydride It should be understood that the tetracarboxylic acids, the esters and half esters of the dianhydrides listed in Table IV will be equally as suitable for use in the present invention. The ester and half ester substituents may be selected from aromatic, e.g. phenyl, or aliphatic, e.g. 1 to 4 carbon atoms, groups. As used in this context, the expression ester means that all four tetracarboxylic acid groups have aromatic or aliphatic substituent groups, while half ester means that only two of the tetracarboxylic acid groups have aromatic or aliphatic substituent groups.

Reaction of the prepolymer to form the polymeric product occurs through the alicyclic endo end capping compounds. While the exact mechanism of the polymeric reaction is not known, it is postulated that a three-dimensional polymer is formed when the prepolymer is subjected to temperatures from approximately 230 C. to 370 C. for up to 4 hours. Although it is not necessary for cure, it has been discovered that the application of up to 700 atmospheres is beneficial in removing voids with the resultant improvements in product properties. The cure times, temperatures, and pressures are variables which depend on the composition, mass, and shape of the article being produced. 'For example, the cure for a large mass of neat resin may require a lower temperature applied for a longer period of time at higher pressure in order to avoid cracking, incomplete consolidation, or voids, than a thin impregnated glass laminated article or a smallarticle containing up to by weight of inert fillers, such as inorganic salts, metals, or other common filler materials.

While it is preferred that the terminal groups used on the prepolymers of this invention constitute only the alicyclic endo compounds, it has been found that up to about one half of the alicyclic endo compound can be replaced by an olefinic compound, such as ethylene diisocyanate without materially altering the properties of many of the polymers. Ideally, this provides a prepolymer with a diaminoethylene radical end cap at one end of the prepolymer chain and an alicyclic endo end cap at the other.

In order to enhance product properties, crosslinking agents may be incorporated into the polymer chain. Solid or liquid organic compounds having olefinic unsaturation to give a solution of amide-acid prepolymer. The dimethylformamide varnish is stripped of solvent and acetic acid/ acetic anhydride by evaporation on a rotary evaporator under vacuum at 150 C. to give a dry powder. A ceramic dish containing the powder is placed in an oven can be added to the initial starting materials while gaseous at 350 C. for 30 minutes and then cooled to room organic olefins are introduced into the starting material temperature. Abrown, rigid, thermoset polymer is formed. by reaction under pressure up to about 3000 p.s.i. Nor- We claim: mally, an amount of crosslinking agent equivalent up to 1. A method of making a prepolymer comprising re- 10% by weight of resin at initiation of cure is used. 10 acting in the presence of an organic solvent proper stoi- Specific examples of a few of the gaseous olefinic cornchiometric amounts of: pounds which are suitable crosslinking agents are ethylene, (A) an aromatic tetraamine; propylene, halogenated ethylene, halogenated propylene, (B) an organic compound containing functional tetraand halogenated butadiene. Specific examples of liquid carboxylic groups capable of reacting with said tetraolefinic compounds which are suitable crosslinking agents amine; are styrene, cyclopentadiene, furane, crotonic acid, acrylic (C) an end cap compound comprising a substituted acid and halogenated, phenyl substituted, or methyl subalicylic endo compound having the formula: stituted forms thereof. Specific examples of a few of the solid olefinic compounds which are suitable crosslinking y, agents for purposes of this invention are tetraphenylcyclo- 2O m Z Z pentadiene, maleic acid and derivatives, cinnamic acid, I I and stilbene. In addition to the gaseous, liquid, or solid Y I Y crosslinking agents, crosslinkings sites may be built into 4 a the polymer chain by the use of polymer reactants having Y6 olefinic substituents; for example a polyimidazopyrrolone made from stilbene tetraamine or styrene dianhydride. to give a p p y r having 1 to 20 repeating units, Furthermore, it should be readily apparent to those Whfifein Y1 Y6 inclusive, i8 Sfilected from the group skilled in the art that various combinations of the above consisting of hydrogen, halOgen, Him), y alkyl li kj agents may b d having 1 to 6 carbon atoms, alkyl ether having 1 to 6 The following examples are illustrative of the procedures Carbon atoms, and y X is Selected from the d to qi hi i i group1 clonsistingbof carbonyl, oxygen, sulfur, methyl- PREPARATION OF THE END CAP ene, a ogen su stituted methylene, alkyl substituted methylene, and aryl substltuted methylene; Z is Example I selected from the group consisting of an aryl ene Approximately 2.5 grams of 3,6-endomethylene-1,2,3,6- radlcal ar} alkylene radical having 0 cartetrahydrophthalic chloride and 0.5 gram of hydrazine hygg gz g g i 9 g g??? of drate are mixed in 50 cc. of absolute ethanol and refluxed 2 7 e as F mm for 6 hours. The mixture is cooled then, and crystals the.grou%cons.lsnng of an Socyanate i and precipitate from solution. The crystals are washed in g g% tempgramm range of 10 to water and ethyl ether. The crystals are placed in a rapidly h d an a stirring chilled solution of cc. of ice water, 10 cc. mung i temperatures rangmg from of 6 N hydrochloric acid, 50 cc. of ethyl ether and 4 0a out 200 grams of sodium nitrate in 15 cc. of water. Cracked ice A methoii of makmg a pripolymer accordmg to is added if necessary to keep the temperature below Glenn 1 wherein the tetracarboxyllc compound is a than- C. After about 20 minutes, the stirring is stopped and 40 g j f' m d f the ether is extracted from the aqueous phase. The aque- 613i 1 fif q pepolymer acfzordmg to ous phase is washed with two 50 cc. portions of ether este? rem e etracar 0 compound 15 a Pheny1 and the combined ether extracts are distilled nearly to 4 method f ki 1 dryness. The solid residue is dissolved in 50 cc. of warm 5O claiin 1 he 2 i ymer ac.cordmg to water, the solution filtered, and the filtrate is distilled to h H rem e e racar 1c ccmpound 1S a PhmyI dryness. Recrystallization of 3,6-endomethylene-1,2-dihy- 2 h d dro-l,2-phenylenediamine is carried out in hot absolute met 0 of makmg a prepqlymer accordlilg to ethanolclaim wherein the tetracarboxyhc compound is an aliphatic ester having 1 to 4 carbon atoms. PREPARATION OF THE PREPOLYMER A method of making a prepolymer according to AND POLYMER clfium lhvsllierein tkllie tetracarboxylic compound is an alip atic a ester aving 1 to 4 carbon atoms. Example H A method of making a prepolymer according to Approximately 25 grams f 3,6 end0methy1ene 1,2-di claim 1 wherein the olefinic crosslinking agent is added. hydro-1,2-phenylenediamine, approximately 4.5 grams of A methqd of maklllg a P p y aCCOIdiHg 0 pyromellitic dianhydride, and 2.2 grams of 3,3'-diamino- Flalm 1 Wherem P to half of the find p compound benzidine are slurried in 200 ml. of dimethylformamide. 1S replaced y ethylene dllsocyallam Approximately 20 grams of acetic anhydride is added to 9. A thermosetting polyimidazopyrrolone having the the solution. The resulting mixture is stirred for 3 hours formula:

Y K A 1 W W i Y \I/Y. N N YGV 4 wherein R is a tetravalent radical selected from the group consisting of aliphatic and aromatic; R is a tetravalent aromatic radical; Y Y inclusive, is selected from the group consisting of hydrogen, halogen, nitro, aryl, alkyl having 1 to 6 carbon atoms, alkyl ether having 1 to 6 carbon atoms, and alkaryl; X is selected from the group consisting of carbonyl, oxygen, sulfur, methylene, halogen substituted methylene, alkyl substituted methylene, and aryl substituted methylene; Z is selected from the group consisting of arylene and an alkylene radical having 0 to 1 carbon atoms; Y is selected from the group consisting of an isocyanate radical and an amino radical, and n is an integer of from 1 to 20.

10. A prepolymer according to claim 9 wherein up to one-half of the end cap compound is replaced by ethylene diisocyanate.

11. A prepolymer according to claim 9 wherein an olefinic crosslinking agent is added.

12. A resin product comprising curing the prepolymer of claim 9.

UNITED STATES PATENTS 3,528,950 9/1970 Lubowitz 26078.4 3,549,594 12/ 1970 TWilley 26047 1,944,731 lO/1933 Diels et al 26()346.6 3,523,151 4/1970 Steinberg 264210 JOSEPH L. SCHOFER, Primary Examiner J. KIGHT, Assistant Examiner US. Cl. X.R.

26032.6 N, 47 CB CZ CP, 77.5 R, 78 R TF UA SC, 78.4 D, 282 

